Repeaters that relay and amplify wireless signals transmitted between base stations and mobile stations may be placed in wireless communication systems depending on the communication environment. The placement of repeaters allows for improvements in the communication state in areas where radio waves from base stations are difficult to receive, and also allows an increase in the cover area of a base station instead of setting up a new base station.
A commonly used type of repeater is the Amplify and Forward (AF) type. The AF type simply amplifies and relays received radio waves using an amplifier installed in the device without demodulating or regenerating the received signals.
It is difficult for repeaters to output radio waves with the quality, which is defined by signal to interference and noise power ratio (SINR), higher than that of received radio waves because the repeaters also amplify interference waves at the same time. However, since the structure is simple and manufacturing cost may be reduced, the AF repeaters have been widely used.
Related art discloses a repeater for changing the antenna pattern of radio wave to be transmitted in response to the position of a radio terminal (for example, see Japanese Laid-open Patent Publication No. 2010-93385). Further, a technique used in a relay station has been proposed that increases/decreases its cover area due to control from the base station according to wireless terminal traffic variation (for example, see Japanese Laid-open Patent Publication No. 2006-197264).
Repeaters are installed in locations so that the base station service areas may be expanded, but the service areas of the repeaters are fixed at the time of installation. As a result, changing the direction and the like of the service area of a repeater requires manual adjustment (e.g., changing the direction of the antenna of the repeater and the like), and the fact that conventional repeaters may not be able to autonomously change the position of the service area is a problem.